The determination of glucose in body fluids, such as urine or blood, is of importance not only in the case of diabetic patients who must control their sugar input, but it is also important in those situations in which the detection of disease as a public health measure requires the screening of the urine or blood of large numbers of people. Because early diagnosis and continued control are so important in diabetes, a glucose test, to be of greatest value to the physician in his diagnosis and control of the disease, must be conveniently rapid, simple enough to serve the clinician and sensitive enough to reflect meaningful variations in urine or blood glucose.
A number of methods exist for measuring or estimating the amount of reducing sugars in body fluids. Some older methods were based on the use of alkaline copper solutions which were heated with the material being tested to precipitate cuprous oxide. These older methods have the disadvantage that their use requires a certain amount of skill and familiarity with the use of measuring equipment and in general do not meet the desiderata of simplicity, accuracy and economy.
Diagnostic tablet procedures, as described in U.S. Pat. No. 2,387,244, found wide usage because of the fact that such procedures could be executed by unskilled persons and the procedures provided an inexpensive, quick, convenient method for the daily testing of urine. While the use of a diagnostic tablet was superior to older techniques, heat was still necessary to perform a test and this meant that a certain degree of care had to be exercised in the compounding and subsequent handling of compositions to eliminate the possibility of unintentional generation of heat by accidental wetting of the diagnostic tablet.
With the development of reagent strips having impregnated areas containing a reagent system including glucose oxidase, peroxidase and a chromogen indicator system, a significant and important breakthrough for achieving a simple, rapid and convenient method for the detection and estimation of the presence of glucose in fluids was achieved. As described, for example, in U.S. Pat. Nos. 2,981,606; 3,092,465; 3,164,534 and 3,298,789 semiquantitative measurement of blood glucose is achieved using reagent strips having a test system based on the enzymatic reaction of glucose oxidase. The use of such test strips provides the user with immediate estimation of the glucose content of a blood sample, and when used in conjunction with a reflectance colorimeter, quantitative results are obtainable which are fully comparable with older and more difficult laboratory procedures.
There are indications, however, that certain of the chromogen indicators which have been used in the past in such reagent strips may be tumorigenic or mutagenic. Among the suspected compounds are such materials as o-tolidine, benzidine, and 2,7-diamino fluorene, all of which have been used as chromogen indicators for indicating the presence of glucose in fluids. Indicator systems have been sought which are safer to use than some of the older indicators and which are at least equally effective.